KR20150017433A - Zero voltage switching full-bridge dc-dc converter - Google Patents

Abstract

A DC-DC converter is disclosed. The DC-DC converter comprises; a full-bridge DC-AC converter which receives DC power and outputs the DC power as AC power by using four switches; a resonance unit including an inductor and a capacitor; a transformer unit which induces voltage which is applied to a first wire according to a switching operation of the four switches into a second wire; and a rectification unit which rectifies the voltage outputted from the transformer unit and outputs it as DC voltage. The present invention enables to perform the zero voltage switching in a wide load range and improves efficiency by reducing switching loss. Therefore, the miniaturization of a power conversion device can be realized by performing the high frequency switching which is limited by the switching loss.

Description

[0001] ZERO VOLTAGE SWITCHING FULL-BRIDGE DC-DC CONVERTER [0002]

The present invention relates to a zero voltage switching full-bridge dc-dc converter, and more particularly to a zero voltage switching full-bridge dc-dc converter operable in a wide load range.

Background Art [0002] With the recent miniaturization of electronic devices, power converters that supply power to electronic devices have also been required to be miniaturized. In order to miniaturize the power converter, high frequency switching is indispensably required. However, when the switching frequency is increased, the efficiency of the power converter is extremely reduced due to the switching loss of the power semiconductor device.

Zero Voltage Switching, Zero Current Switching, and Resonant Converter are examples of methods for reducing the switching loss of the power semiconductor device. Soft switching devices are generally referred to as soft switching devices. I call it.

However, the conventional soft switching greatly differs in characteristics depending on the load conditions, making it difficult to obtain a soft switching effect in a wide load range. Therefore, there is a demand for a power conversion device having a soft switching effect even in a wide load range.

Accordingly, it is an object of the present invention to provide a zero voltage switching full-bridge dc-to-dc converter operable in a wide load range.

According to an aspect of the present invention, there is provided a DC-DC converter including: a DC-DC converter for receiving a DC power source and outputting the input DC power through an AC power source using four switches; A resonance unit including a converter, an inductor and a capacitor, a transformer for converting a voltage applied to the primary winding into a secondary winding according to a switching operation of the four switches, and a transformer for rectifying the voltage output from the transformer, And outputting the voltage as a voltage.

In this case, the DC-AC converter includes a first switching unit including a first switch and a second switch serially connected from a power source to ground, and a second switching unit connected in parallel with the first switching unit, Wherein one end of the primary side winding of the transformer is commonly connected to the other end of the first switch and one end of the second switch, And the other end of the negative primary winding can be commonly connected to the other end of the third switch and one end of the fourth switch.

In this case, when both of the first switch and the second switch are turned off, the resonance unit may make the both-end voltage of the first switch and the both-end voltage of the second switch have zero voltage.

The DC-DC converter controls the first switching unit such that the first switch and the second switch are alternately switched, and the second switch unit is controlled so that the third switch and the fourth switch are alternately switched, And a control unit for controlling the display unit.

In this case, when the first switch is changed from the on state to the off state, the control unit turns on the second switch in the off state after a predetermined first time, and when the second switch changes from the on state to the off state , It is possible to turn on the first switch in the off state after a predetermined second time.

Meanwhile, the first switch, the second switch, the third switch, and the fourth switch may be MOSFETs.

In this case, the MOSFET has an output capacitor, and the resonance part can discharge the charged electric charge of the output capacitor when both the first switch and the second switch are off.

The first switch is connected in common to one end of the power source and the third switch and the other end is commonly connected to one end of the transformer, the second switch, and the resonator, One end of the first switch is commonly connected to one end of the other end of the first switch, the transformer and the resonator, and the other end is commonly connected to the other end of the ground, the fourth switch, and the other end of the resonator.

In this case, the resonance portion includes a first inductor whose one end is connected to the other end of the first switch, one end of the second switch, and the transformer portion, and one end is connected to the other end of the inductor, And a capacitor whose other end is commonly connected to the other end of the second switch, the other end of the fourth switch, and the ground.

In this case, the transformer may include a second inductor whose one end is commonly connected to the other end of the first switch, one end of the second switch, and one end of the first inductor, And the other end of the primary winding is commonly connected to the other end of the third switch and the one end of the fourth switch and the secondary winding is connected to the rectifying unit .

In this case, the biphasic second inductor may be the leakage inductance of the transformer.

As described in detail above, the present invention contemplates a full-bridge DC-DC converter circuit with a new zero voltage switching circuit to enable zero voltage switching in a wide load range, thereby reducing switching losses and improving efficiency Frequency switching, which is limited by the switching loss, can be achieved, and thus miniaturization of the power conversion device can be achieved.

Therefore, when the circuit designed in the present invention is applied to a power supply for a computer server, a power supply for a portable apparatus, a display, and an illumination circuit, efficiency improvement and miniaturization of the apparatus can be obtained.

1 is a block diagram illustrating a configuration of a zero voltage switching full-bridge DC-DC converter according to an embodiment of the present invention;
2 is a circuit diagram of a zero voltage switching full-bridge DC-DC converter according to a first embodiment of the present invention,
FIG. 3 is a switch waveform diagram for circuit operation of the zero voltage switching full-bridge DC-DC converter according to the first embodiment,
FIGS. 4 to 11 are diagrams showing current paths of the DC-DC converter in each time process of FIG. 3;
12 is a circuit diagram of a zero voltage switching DC-DC converter according to the second embodiment,
13 is an operational waveform diagram of the DC-DC converter of FIG. 2 when the load condition is 50%, and FIG.
14 is an operational waveform diagram of the DC-DC converter of FIG. 2 when the load condition is 5%.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a block diagram showing the configuration of a zero-voltage switching full-bridge DC-DC converter (hereinafter referred to as a DC-DC converter) according to an embodiment of the present invention.

Referring to FIG. 1, the DC-DC converter 100 may include a DC-AC converter 110, a resonator 120, a transformer 130, a rectifier 140, and a controller 150.

The DC-AC converter 110 (or the DC-AC converter) is a full-bridge DC-AC converter that receives DC power and outputs the input DC power to the AC power using four switches. Specifically, the DC-AC converter 110 includes a first switching unit 111 and a second switching unit 115 connected in parallel to a power source. Here, each of the first switching unit 111 and the second switching unit 115 includes two switches (for example, a first switch and a second switch or a third switch and a fourth switch) series-connected from the power source to the ground And each of the switching units 111 and 115 can generate a pulse-like voltage having a predetermined frequency by alternately switching the plurality of internal switches. A specific configuration of the DC-AC converter 110 will be described later with reference to Fig. Here, the first to fourth switches may be MOSFETs, which are power semiconductor switches, and may be semiconductor devices such as IGBT, SiC, and GaN transistors.

The resonance unit 120 is connected in parallel with the first switch and / or the second switch of the DC-AC converter 110. When both the first switch and the second switch are turned off, both ends of the first switch and the second switch So that the voltage across the switch has a zero voltage. A specific configuration of the resonator 120 will be described with reference to Fig. In the above description, the resonator unit 120 is described as being connected to the first switch and / or the second switch. However, the resonator unit 120 may be connected in parallel with the third switch and / or the fourth switch .

The transformer 130 induces a voltage applied to the primary winding in accordance with the switching operation of the DC-AC converter 110 as a secondary winding. A concrete configuration of the transformer 130 will be described with reference to FIG.

The rectifying unit 140 rectifies the voltage output from the transformer 130 and outputs the rectified voltage as a DC voltage. Specifically, the rectifying unit 140 may be implemented by a full-bridge rectifier as shown in FIG. 2, or may be implemented by a center-tap rectifier as shown in FIG.

The control unit 150 controls the DC-AC converter 110 such that the first switch 112 and the second switch 113 in the first switching unit 111 are alternately switched. The control unit 150 controls the DC-AC converter 110 such that the third switch 116 and the fourth switch 117 in the second switching unit 115 are alternately switched. Specifically, the controller 150 alternately switches the first switch and the second switch (or the third switch and the fourth switch) so that both of the switches are turned off for a predetermined time in order to prevent an arm short and secure a zero voltage switching period Switch to the target. For example, when the first switch is changed from the on state to the off state, the controller 150 turns on the second switch after a predetermined first time, and when the second switch is changed from the on state to the off state, The first switch can be turned on after the set second time (i.e., after the dead time). Here, the predetermined first time and the predetermined second time may be the same or different. When the third switch is changed from the on state to the off state, the controller 150 turns on the fourth switch after a predetermined first time, and when the fourth switch is changed from the on state to the off state, After the time, the third switch can be turned on. The switching control of the first to fourth switches of the specific controller 150 may be as shown in FIG.

As described above, the DC-DC converter 100 according to the present embodiment includes the resonance unit 120 that converts the voltages across the first switch to the fourth switch to 0 voltage when the first switch and the second switch are open, So that zero voltage switching can be performed regardless of the load condition.

2 is a circuit diagram of a zero voltage switching DC-DC converter according to a first embodiment of the present invention.

DC-AC converter 110 is a full-bridge DC-AC converter. The full-bridge DC-AC converter 110 is composed of a first switch 112 connected in series and a third switch 116 and a fourth switch 117 connected in series with the second switch 113.

The first switch 112 selectively switches according to a control signal provided from the controller 150. Specifically, the first switch 112 is commonly connected to the DC power source and one end of the third switch 116, and the other end is connected to one end of the second switch 113, And one end of the primary winding of the transformer (130). Here, the first switch 112 may be implemented as a MOSFET, wherein an anti-parallel body diode and an equivalent capacitance Co1 exist between the drain and the source. In this embodiment, the first switch is implemented as a MOSFET. However, the first switch may be formed using a semiconductor device such as an IGBT, a SiC, or a GAN transistor.

The second switch 113 selectively switches according to a control signal provided from the controller 150. Specifically, the second switch 113 is connected in common to one end of the first switch 112, one end of the resonator 120 and one end of the primary winding of the transformer 130, Is commonly connected to the other end of the DC power source, the other end of the resonance unit 120, and the other end of the fourth switch 117. Here, the second switch 113 may be implemented as a MOSFET. In this case, an anti-parallel body diode and an equivalent capacitance Co4 exist between the drain and the source. In this embodiment, the second switch is implemented as a MOSFET. However, the second switch may be formed using a semiconductor device such as an IGBT, SiC, or GaN transistor.

The third switch 116 selectively switches according to a control signal provided from the controller 150. Specifically, the third switch 116 is connected in common to one end of the DC power source and the first switch 112, and the other end is connected to one end of the fourth switch 117 and the first end of the transformer 130 And is commonly connected to the other end of the winding. Here, the third switch 116 may be implemented as a MOSFET, wherein an anti-parallel body diode and an equivalent capacitance Co2 exist between the drain and the source. In this embodiment, the third switch is implemented as a MOSFET. However, a third switch may be formed using a semiconductor device such as an IGBT, a SiC, or a GaN transistor.

The fourth switch 117 selectively switches according to a control signal provided from the controller 150. Specifically, the fourth switch 117 is commonly connected to the other end of the third switch 116 and the other end of the primary winding of the transformer 130, and the other end is connected to the other end of the DC power source, And the other end of the second switch 120 and the other end of the second switch 113. Here, the fourth switch 117 may be implemented as a MOSFET, wherein an anti-parallel body diode and an equivalent capacitance Co3 exist between the drain and the source. In this embodiment, the fourth switch is implemented as a MOSFET. However, the fourth switch may be formed using a semiconductor device such as an IGBT, a SiC, or a GaN transistor.

The resonator unit 120 includes a first inductor 121 and a capacitor 122 connected in series. In the illustrated example, the first inductor 121 is connected to the upper part and the capacitor 122 is connected to the lower part. However, in the embodiment, the capacitor 122 is connected to the upper part and the first inductor 121 is connected to the lower part. May be implemented in the form of being connected.

One end of the first inductor 121 is commonly connected to the other end of the first switch 112 and one end of the second switch 113 and the transformer 130 and the other end of the first inductor 121 is connected to the capacitor 122 .

One end of the capacitor 122 is connected to the other end of the first inductor 121 and the other end is commonly connected to the other end of the second switch 113 and the other end and the ground of the fourth switch 117.

며, 안정된 영전압 스위칭 동작을 위해서는 공진 주파수를 스위칭 주파수보다 충분히 낮게 설정하는 것이 바람직하다. The resonance frequency of the resonance portion 120 is

And for the stable zero voltage switching operation, it is desirable to set the resonance frequency sufficiently lower than the switching frequency.

The transformer 130 includes a second inductor 131 and a transformer 132.

The second inductor 131 is a leakage inductance of the transformer 132. Specifically, the second inductor 131 is connected in common to one end of the first switch 112, one end of the second switch 113 and one end of the resonator 120, and the other end of the second inductor 131 is connected to the transformer 132). ≪ / RTI >

The transformer 132 includes a primary coil and a secondary coil, and the voltage applied to the primary side is proportional to the winding ratio of the transformer 132, that is, when the winding ratio of the transformer is N: 1 / N times the applied voltage is applied to the secondary side winding. One end of the primary coil of the transformer 132 is connected to the other end of the second inductor 131 and the other end of the primary coil is connected to the other end of the third switch 116 and the other end of the fourth switch 117, To the other end. The secondary coil of the transformer 132 is connected to the rectifying unit 140. On the other hand, when the secondary side rectifying part 140 is a center tap rectifier, the center of the secondary coil can be connected to the ground of the output terminal.

The rectifying unit 140 rectifies the voltage (specifically, the high frequency AC voltage) output from the transformer 132 and outputs it as a DC voltage. In particular, the rectifier 140 may be implemented as a full-bridge rectifier and may be implemented with a center-tap rectifier.

2, the rectifying unit 140 includes a first diode 141, a second diode 142, a third diode 143, a fourth diode 144, and a third diode 144. The rectifier 140 includes a first diode 141, a second diode 142, a third diode 143, An output inductor 145, and an output capacitor 146.

The first diode 141 has an anode connected in common to one end of the secondary coil of the transformer 132 and a cathode of the fourth diode 144 and a cathode connected in common to the cathode of the second diode 142 and the output inductor 145, And is connected in common to one end of the battery.

The second diode 142 is connected in common to the other end of the secondary coil of the transformer 132 and the cathode of the third diode 143 and the cathode is connected to the cathode of the first diode 141 and the output inductor 145, Respectively.

The third diode 143 is connected in common to the anode of the fourth diode 144 and the other end of the output capacitor 146 and the cathode is connected to the other end of the secondary coil of the transformer 132 and the other end of the second diode 142, Is commonly connected to the anode of the transistor.

The anode of the fourth diode 144 is connected in common to the anode of the third diode 143 and the other end of the output capacitor 146 and the cathode is connected to one end of the secondary coil of the transformer 132 and the other end of the first diode 141, Is commonly connected to the anode of the transistor.

The output inductor 145 and the output capacitor 146 smooth the rectified voltage in the first to fourth diodes. Specifically, one end of the output inductor 145 is commonly connected to the cathode of the first diode 141 and the cathode of the second diode 142, and the other end is connected to one end of the output capacitor 146.

One end of the output capacitor 146 is connected to the other end of the output inductor 145 and the other end is commonly connected to the anode of the fourth diode 144 and the anode of the third diode 143. Where the voltage across the output capacitor 146 is the output voltage of the dc-dc converter.

In the illustrated example, the rectifying unit 140 is implemented using a full-bridge rectifier. However, the rectifying unit 140 may be implemented by a center-tap rectifier as shown in FIG.

The configuration and circuit of the DC-DC converter 100 according to the first embodiment have been described above. Hereinafter, the DC-DC converter 100 according to the operation of the DC-AC converter 110 will be described with reference to FIG. 2 and FIG. The operation of transferring the energy of the battery is explained.

FIG. 3 is a switch waveform diagram for circuit operation of the zero voltage switching full-bridge DC-DC converter according to the first embodiment.

3, voltages Vg1, Vg2, Vg3, and Vg4 are gate pulse waveforms for driving the first switch M1, the second switch M2, the third switch M3, and the fourth switch M4, which are MOSFET switches, to be. Each gate pulse waveform has a duty ratio of 50%, and Vg1 and Vg4, and Vg2 and Vg3 have switching states that are opposite to each other. Between Vg1 and Vg2, Vg3 and Vg4 waveforms, each leg is prevented from shorting during converter operation and dead time Td for zero voltage switching is given. A phase delay Tpd is given between the gate pulses Vg1 and Vg3, and since Vg2 and Vg4 are complementary outputs of Vg1 and Vg3, the same phase delay is given between the two waveforms.

FIG. 4 is a diagram showing a current path in a period t0-t1 of FIG. 3. FIG.

4, when the first switch 112, the second switch 113 and the third switch 116 are in the OFF state and the fourth switch 117 is in the ON state, The DC power source 101 or the input power source, the first switch 112, the second inductor 131, the primary winding of the transformer 132, the first current path that flows through the fourth switch 117, .

The current in the primary winding of the transformer 132 changes the current in the secondary winding of the transformer 132 so that the secondary winding of the transformer 132, the first diode 141, the output inductor 145, A second current path through the output capacitor 146 and the third diode 143 is formed.

At this time, the resonance current in the resonance part 120 flows, and the current flowing in the first inductor 121 and the voltage flowing in the capacitor 122 are increased.

When the fourth switch 117 is turned off in such a switch state, the current path is changed to the current path shown in Fig.

FIG. 5 is a diagram showing a current path in a period from t1 to t2 in FIG.

5, when the second switch 113 and the third switch 116 are in the OFF state and the fourth switch 117 is off when the first switch 112 and the fourth switch 117 are ON, A current path is formed between the drain-source equivalent capacitance Co2 of the first switch 112 and the third switch 116 by the second inductor 131 and the current path is formed between the second switch 116 and the second switch 116. [ The voltage charged in the drain-source equivalent capacitance Co2 is discharged to be zero, which causes the anti-parallel body diode of the third switch 116 to be turned on.

In this period, the input voltage vi is continuously applied to the first inductor 121 and the capacitor 122 to cause the resonance current to flow.

When the third switch 116 is turned on in such a switch state, the current path is changed to the current path shown in Fig.

Fig. 6 is a diagram showing a current path in the section from t2 to t3 in Fig. 3. Fig.

6, when the second switch 113, the third switch 116 and the fourth switch 117 are in the OFF state and the first switch 112 is in the ON state and the third switch 116 is in the ON state State, the voltage across the third switch 116 is zero, so that zero voltage switching is performed.

During this period, a current flows from the source to the drain of the third switch 116.

In this period, the input voltage vi is continuously applied to the first inductor 121 and the capacitor 122, and the resonance current flows.

When the first switch 112 is turned off in such a switch state, the current path is changed to the current path shown in Fig.

Fig. 7 is a diagram showing a current path in a period from t3 to t4 in Fig. 3. Fig.

7, when the second switch 113 and the fourth switch 117 are in the OFF state and the first switch 112 and the third switch 116 are in the ON state, the first switch 112 is turned off The current path through the drain-source capacitance Co4 of the second switch 113 is formed by the first inductor 121 and the second inductor 131. [ The voltage charged to the drain-source capacitance Co4 through the current path is discharged to be zero, whereby the anti-parallel body diode of the second switch 113 is conducted.

On the other hand, in discharging the drain-source capacitance Co4, the current is also discharged in the currents flowing in the first inductor 121 and the second inductor 131, and the current flowing in the resonance unit 120 is So that drain-source capacitance (Co4) can be discharged quickly even at low load currents.

When the second switch 113 is turned on in such a switch state, the current path is changed to the current path shown in Fig.

FIG. 8 is a diagram showing a current path in a period from t4 to t5 in FIG. 3; FIG.

8, when the first switch 112, the second switch 113 and the fourth switch 117 are off and the third switch 116 is on, the second switch 113 is turned on State, the both-end voltage of the second switch 113 is zero, so that zero voltage switching is performed.

The DC power source 101, the third switch 116, the primary winding of the transformer 132, the second inductor 131, and the third switch 116 are turned on during this period, , A third current path that flows through the second switch 113 is formed. At this time, an - input voltage is applied to the primary winding of the transformer 132.

The current in the primary winding of the transformer 132 changes the current in the secondary winding of the transformer 132 so that the secondary winding of the transformer 132, the second diode 142, the output inductor 145, A fourth current path through the output capacitor 146 and the fourth diode 144 is formed.

At this time, a resonance current flows through the second switch 113 due to the voltage charged in the capacitor 122 of the resonance unit 120.

When the third switch 116 is turned off in such a switch state, the current path is changed to the current path shown in Fig.

FIG. 9 is a diagram showing a current path in a period from t5 to t6 in FIG. 3; FIG.

9, when the first switch 112 and the fourth switch 117 are in the OFF state and the second switch 113 and the third switch 116 are in the ON state, the third switch 116 is turned off A current path is formed between the drain-source equivalent capacitance Co3 of the second switch 113 and the fourth switch 117 by the second inductor 131 and the current path is formed between the drain- The voltage charged in the drain-source equivalent capacitance Co3 is discharged to be zero, thereby causing the anti-parallel body diode of the second switch 113 to be turned on.

In this section, a resonance current flows through the second switch 113 by the voltage charged in the capacitor 122 to the first inductor 121 and the capacitor 122.

When the fourth switch 117 is turned on in such a switch state, the current path is changed to the current path shown in Fig.

Fig. 10 is a diagram showing a current path in a section from t6 to t7 in Fig. 3. Fig.

10, when the first switch 112, the third switch 116 and the fourth switch 117 are off and the second switch 113 is on and the fourth switch 117 is on State, the both-end voltage of the fourth switch 117 is zero, so that zero voltage switching is performed.

During this period, a current flows from the source to the drain of the fourth switch 117.

In this section, the resonance unit 120 continuously flows the resonance current through the second switch 113 by the voltage charged in the capacitor 122. [

In such a switch state, the second switch 113 is switched to the OFF state and changed to the current path as shown in FIG.

11 is a diagram showing a current path in a period from t7 to t8 in Fig.

11, when the first switch 112 and the third switch 116 are OFF and the second switch 113 and the fourth switch 117 are ON and the second switch 113 is OFF, The current path through the drain-source capacitance Co1 of the first switch 112 is formed by the first inductor 121 and the second inductor 131. [ The voltage charged in the drain source capacitance Co1 of the first switch 112 through this path is discharged to be zero, which causes the anti-parallel body diode of the first switch 112 to be turned on.

In discharging the drain source capacitance Co1 of the first switch 112 as well as the current flowing in the first inductor 121 of the resonance part 120 as well as the second inductor 131 of the transformer 130 Since the current flowing in the resonance unit 120 is independent of the load current, the discharge can be performed even at a low load current in a short period of time.

4 to 11, the primary side voltage is transmitted to the secondary side in the period t0-t1 (FIG. 4) and the period t4-t5 (FIG. 8) The duty ratio is expressed by Equation (1).

Where D is the effective duty ratio, Td is the dead time for zero voltage switching, Tpd is the upper right delay, and Ts is the switching period.

At this time, the output voltage of the DC-DC converter 100 can be expressed by Equation (2).

As described above, the four switches in the DC-AC converter in the DC-DC converter according to the present embodiment can switch under the condition that the drain-source voltage is zero, thereby greatly reducing the switching loss and thereby enabling high frequency switching. Particularly, during the zero voltage switching of the MOSFET switches M1 and M4, the first inductor and the capacitor of the resonator 120 are rapidly discharged, and the discharging operation of this circuit is independent of the load condition. Switching can be realized.

12 is a circuit diagram of a zero voltage switching DC-DC converter according to the second embodiment. Specifically, the DC-DC converter 100 'according to the second embodiment is an embodiment in which the rectifying part 140' is implemented using a center-tap rectifier.

The configuration of the DC-AC converter 110 and the resonator unit 120 except for the transformer 130 'and the rectifier unit 140' in the DC-DC converter 100 'according to the second embodiment is the same as that of the first embodiment The description of the DC-AC converter 110 and the resonator unit 120 is omitted.

The transformer 130 'is composed of a second inductor 131 and a transformer 132'.

The second inductor 131 is the leakage inductance of the transformer 132 '. Specifically, the second inductor 131 is connected in common to one end of the first switch 112, one end of the second switch 113 and one end of the resonator 120, and the other end of the second inductor 131 is connected to the transformer 132 ').

The transformer 132 'includes a primary coil and a secondary coil, and the voltage applied to the primary side is proportional to the winding ratio of the transformer 132', that is, when the winding ratio of the transformer is N: 1 / N times of the voltage applied to the secondary winding is applied to the secondary winding.

One end of the primary coil of the transformer 132 'is connected to the other end of the second inductor 131 and the other end of the primary coil of the transformer 132' is connected to the other end of the third switch 116 and the other end of the fourth switch 117 They are commonly connected to one end. The secondary coil of the transformer 132 'is connected to the rectifying part 140', and the center of the secondary coil is connected to the ground of the output terminal.

The rectification section 140 'is composed of a fifth diode 147, a sixth diode 148, an output inductor 145 and an output capacitor 146.

The fifth diode 147 and the sixth diode 148 rectify the voltage output from the transformer 132 '.

The fifth diode 147 has its anode connected to one end of the secondary coil and its cathode connected in common with one end of the cathode of the second diode 148 and the output inductor 145.

The cathode of the sixth diode 148 is connected to the cathode of the fifth diode 147 and one end of the output inductor 145 in common.

The output inductor 145 and the output capacitor 146 smooth the voltage rectified in the fifth diode 147 and the sixth diode 148.

FIG. 13 is an operation waveform diagram of the DC-DC converter of FIG. 2 when the load condition is 50%, and FIG. 14 is an operation waveform diagram of the DC-DC converter of FIG. 2 when the load condition is 5%.

13A and 14A, Vi is a DC voltage (400V) to be supplied. Referring to FIGS. 13A and 14A, it is confirmed that a constant DC voltage Vi is supplied.

In Fig. 13B and Fig. 14B, Vg1 is a gate signal (dark solid line) for driving the first switch, and Vg2 is a gate signal (light solid line) for driving the second switch. Referring to FIGS. 13B and 14B, it can be seen that the first switch 112 and the second switch 113 are alternately switched. Also, it can be confirmed that the two switch modes are turned off for a certain time in order to prevent the arm short and to secure the zero voltage switching period.

Vg3 in Figs. 13C and 14C is a gate signal (dark solid line) for driving the third switch, and Vg4 is a gate signal (light solid line) for driving the fourth switch. Referring to FIGS. 13C and 14C, it can be seen that the third switch 116 and the fourth switch 117 are alternately switched. Also, it can be confirmed that the two switch modes are turned off for a certain time in order to prevent the arm short and to secure the zero voltage switching period.

In Fig. 13D and Fig. 14D, VM1 is the drain-source voltage of the first switch and VM2 is the drain-source voltage of the second switch. 13D and 14D, when the first switch 112 is turned off, it can be confirmed that the voltage across the first switch 112 becomes 0 V by the operation of the resonator 120. When the second switch 113 is switched to the off state, it can be confirmed that the voltage across the second switch 113 becomes 0 V by the operation of the resonator 120. [

VM3 in Figs. 13E and 14E is the drain-source voltage of the third switch, and VM4 is the drain-source voltage of the fourth switch. 13E and 14E, when the third switch 116 is switched to the OFF state, it can be confirmed that the voltage across the third switch 116 becomes 0 V by the operation of the resonator 120. When the fourth switch 117 is switched to the OFF state, it can be confirmed that the voltage across the fourth switch 117 becomes 0 V by the operation of the resonator 120. [

13F and 14F are the voltages of the secondary side winding of the transistor, and ILr in Figs. 13G and 14G is the current of the first inductor 121. Fig.

13 and 14, the drain-source voltages of the first to fourth switches are zeroed off before the gate pulse is applied within a wide load range of 5% to 50% Voltage switching.

 In the conventional method, only the leakage inductance Lr is used and zero voltage switching is impossible in a low load range. However, in the circuit designed in the present invention, zero voltage switching is possible even at a low load, and switching loss can be greatly reduced.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the appended claims.

100: DC-DC converter 110: DC-AC converter
120: resonator part 130: transformer part
140: rectification part

Claims (11)

In a DC-DC converter,
A full-bridge DC-AC converter for receiving a DC power source and outputting the input DC power as an AC power using four switches;
A resonance part including an inductor and a capacitor;
A transformer for converting a voltage applied to the primary winding to a secondary winding according to the switching operation of the four switches; And
And a rectifying unit for rectifying a voltage output from the transformer and outputting the rectified voltage as a DC voltage. The method according to claim 1,
The DC-AC converter includes:
A first switching unit including a first switch and a second switch connected in series from a power source to a ground; And
And a second switching unit connected in parallel with the first switching unit and including a third switch and a fourth switch connected in series from the power source to the ground,
One end of the primary winding of the transformer is commonly connected to the other end of the first switch and one end of the second switch,
And the other end of the primary winding of the transformer is commonly connected to the other end of the third switch and one end of the fourth switch. 3. The method of claim 2,
The resonator may include:
DC converter according to claim 1 or 2, wherein when both the first switch and the second switch are turned off, the both-end voltage of the first switch and the both-end voltage of the second switch have a zero voltage. 3. The method of claim 2,
The DC-DC converter includes:
And a control unit for controlling the first switching unit so that the first switch and the second switch are alternately switched and controlling the second switch unit such that the third switch and the fourth switch are alternately switched Features a DC to DC converter. 5. The method of claim 4,
Wherein,
When the first switch is changed from the on state to the off state, the second switch in the off state is turned on after a predetermined first time,
And turns on the first switch in the off state after a predetermined second time when the second switch is changed from the on state to the off state. 3. The method of claim 2,
Wherein the first switch, the second switch, the third switch, and the fourth switch are MOSFETs. The method according to claim 6,
The MOSFET having an output capacitor,
The resonator may include:
And discharges the charged electric charge of the output capacitor when both the first switch and the second switch are turned off. 3. The method of claim 2,
Wherein the first switch comprises:
One end of which is commonly connected to one end of the power source and the third switch, and the other end is commonly connected to one end of the transformer, the second switch and the resonator,
Wherein the second switch comprises:
One end of the first switch is commonly connected to the other end of the first switch, the transformer and the resonator, and the other end is connected in common to the other end of the ground, the fourth switch and the other end of the resonator. - DC converter. 9. The method of claim 8,
The resonator may include:
A first inductor whose one end is commonly connected to the other end of the first switch, one end of the second switch, and the transformer; And
And a capacitor having one end connected to the other end of the inductor and the other end connected in common to the other end of the second switch, the other end of the fourth switch, and the ground. 10. The method of claim 9,
The trans-
A second inductor whose one end is commonly connected to the other end of the first switch, one end of the second switch, and one end of the first inductor; And
One end of the primary winding is connected to the other end of the second inductor, the other end of the primary winding is commonly connected to the other end of the third switch and one end of the fourth switch, And a transformer connected to the DC-DC converter. 11. The method of claim 10,
The second inductor,
And the leakage inductance of the transformer is a leakage inductance of the transformer.

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